This invention relates to device for mixing two components which react with each other and for dispensing the pasty mass mixed therefrom.
U.S. Pat. No. 4,014,463 discloses a device for mixing and dispensing pasty masses in which two components, that are to be blended to from the desired mass, are contained in two compartments of a container. The compartments are disposed axially in series, the rearward compartment being movable like a piston relative to the forward compartment. The component contained in the rearward compartment will flow through a tube axially passing through the forward compartment to exit at the forward end thereof, while the material contained in the forward compartment exits into the annular space defined between the tube and the outer wall of the container opening.
The concentrically extruded material is urged through a static mixer which is adapted to be inserted into the container opening and in which the two components are mixed to form a homogenous pasty mass to be dispensed from the front discharge end of the mixer.
The static mixer is composed in the usual way from a plurality of blade members which are arranged serially with alternating senses of rotation in the discharge direction, the leading edge of each downstream blade member extending normal to the trailing edge of the preceding upstream blade member.
Such devices with static mixers are used particularly in cases where it is important thoroughly to blend two components with each other so as to obtain a pasty mass exhibiting homogeneous properties such as a dental impression compound or a two-component adhesive.
In the known device, the annular area of the container opening has a flexible sealing disk provided therein which is to be opened by the discharge pressure of the respective component while it is to be closed when the pressure is relieved. This is intended to prevent inadvertent mixing of the two components when the dispensing operation is interrupted. Mixing will merely take place in the area outside of the sealing disk and in the static mixer.
Prior to the renewed use of the device the mixer is withdrawn from the container opening and discarded together with the hardened mass left therein, and any residues of the partially mixed and hardened mass are removed from the area of the container opening outside the sealing disk. The mixer is connected to the container by means of a clamping nut which surrounds the mixer casing and is threaded onto the front end of the container.
In the known device, the described sealing disk poses a problem because, on the one hand, it should be as compliant as possible to permit sufficient widening of its central opening surrounding the tube while, on the other hand, it should exhibit sufficiently high restoring forces to seal the opening in the absence of a discharge pressure. In practical use, such a sealing disk will result in an undesired increase of the required discharge pressure.
It is a further drawback of the known device that, after removal of a previously used mixer and prior to renewed use, the remaining hardened mass has to be removed manually from the opening area of the container. This cleaning operation is particularly difficult in the relatively narrow opening area of the internal dispensing tube and can hardly be performed completely. However, any cross-sectional reduction caused by non-removed residues will, upon renewed use, not only lead to a change in the mixing ratio and thus to a deterioration of the properties of the finished mass but also result in an increase in pressure. With certain masses it may even lead to clogging, thereby rendering the entire device inoperative.
Finally, the known device requires a specially configured container which in turn requires considerable efforts in respect of manufacture, filling and assembly. Commonly available filling machines cannot readily be used for filling the known device.